To fully isolate #DB and #BP from instrumentable code it's necessary to avoid invoking the hardware latency tracer on nmi_enter/exit().
Provide nmi_enter/exit() variants which are not invoking the hardware latency tracer. That allows to put calls explicitely into the call sites outside of the kprobe handling. Signed-off-by: Thomas Gleixner <[email protected]> --- include/linux/hardirq.h | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -76,8 +76,16 @@ extern void irq_exit(void); /* * nmi_enter() can nest up to 15 times; see NMI_BITS. + * + * ftrace_count_nmi() only increments a counter and is noinstr safe so it + * can be invoked in nmi_enter_notrace(). ftrace_nmi_handler_enter/exit() + * does time stamping and will be invoked in the actual NMI handling after + * an instrumentable section has been reached. + * + * nmi_enter/exit() still calls into the tracer so existing callers + * wont break. */ -#define nmi_enter() \ +#define nmi_enter_notrace() \ do { \ arch_nmi_enter(); \ printk_nmi_enter(); \ @@ -87,10 +95,15 @@ extern void irq_exit(void); rcu_nmi_enter(); \ lockdep_hardirq_enter(); \ ftrace_count_nmi(); \ + } while (0) + +#define nmi_enter() \ + do { \ + nmi_enter_notrace(); \ ftrace_nmi_handler_enter(); \ } while (0) -#define nmi_exit() \ +#define nmi_exit_notrace() \ do { \ ftrace_nmi_handler_exit(); \ lockdep_hardirq_exit(); \ @@ -102,4 +115,10 @@ extern void irq_exit(void); arch_nmi_exit(); \ } while (0) +#define nmi_exit() \ + do { \ + ftrace_nmi_handler_exit(); \ + nmi_exit_notrace(); \ + } while (0) + #endif /* LINUX_HARDIRQ_H */
